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6. Kelps, Mangroves & Photosynthetic Habitats

  Photosynthetic Habitats

  Kelps   Anatomy   Community   Ecosystem

  Mangroves   Anatomy   Community   Ecosystem

  Other photosynthetic habitats   Seagrasses

Dr Rhian G. Waller 23rd April 2010 Reading:

Photosynthetic Habitats

  Primary Producing Habitats

  Need direct sunlight to survive

  Coastal oceans

  Clear water

  Major Habitat forming:-

  Sea Weeds (kelps)

  Kelps

  Mangrove Trees

  Terrestrial trees

  Sea Grass Beds

  Eelgrass

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Algae

  Photosynthesizing

  Pigments for specific wavelengths

  Red algae can be found deepest

Seaweed Group Pigments Storage Products Light used

Green Algae Chlorophyll a,b Starch Red, blue

Brown Algae Chlorophyll a, c, fucoxanthin Laminarin, Mannitol Red, blue

Red Algae Chlorophyll a, d, phycoerythrin, phycocyanin

Floridan starch Green

Kelps   Brown Algae

  Anatomy   Thallus

  Blade

  Stipe

  Holdfast

  Pneumatocysts

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Kelps   300+ species of Kelp

  Not all create forests

  Some species grow 30cm per day

  Different species of kelp make up the habitat   Community succession

  Taller = more light

  Shorter = survive storms

  Environmental Requirements   Nutrient rich waters

  Upwelling zones

  ~ <20°C

  Arctic & Antarctic

  Clear water

  5 – 15m depth Levinton, 1995

Kelp Communities   Kelps create ecosystems &

sustain specific communities

  Pelagic   Rockfish, Perch

  Nursery habitats   Feeding

  Sea Otters

  Benthic   Holdfast Communities

  Brittle starts, snails

  Canopy Communities   Urchins, abalone, seastars

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Kelp Communities

  Urchins are an important part of the kelp habitat

Sea Urchin Barrens   Urchins usually feed on

“drift algae”

  Storms strip bottom of kelps

  Urchins feed on new kelp recruits   “Roving”

  Can take a year to redevelop kelp beds

  Once kelp developed, urchins stop “roving”

Levinton, 1995

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Killer Whales & Kelp? Whaling

reduces Great Whales

Killer Whales change diet

Eat more Sea Otters

Less Sea Otters = more

urchins

More urchins = more urchin

barrens

Collapse of Alaskan Kelp

forests

Kelps

  Fishery for kelp   Alginate

  Thickener

  Ice cream, jelly

  Fertilizer

  Iodine

  Fuel

  Diet pills!

  Appetite suppression,

Nutrition per 100g (raw)

Energy 43 kcal

Carbohydrates 9.6g

Sugars 0.6g

Fiber 1.3g

Fat 0.6g

Protein 1.7g

Vit. B9 (Folate) 180ug (45%)

Iron 2.8mg (22%)

Magnesium 121mg (33%)

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Mangroves   Terrestrial Trees

  ~50 species “true mangroves”   Live on coastlines

  Tropics & subtropics

  Help to prevent coastal erosion   Stabilize soils

  Invasive…   Buoyant seeds

  Water dispersal

  Seeds can photosynthesize   Travel long distances

Mangroves

  Mangrove roots dissipate wave energy

  Roots slow flow

  Protection from storm surges

  Trap sediment

  Sediment comes in on high tides

  Only fine particles leave on ebb

  Sink for heavy (trace) metals

  Leads to highly saline, anoxic environment

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Mangroves   Salinity Adaptation

  Highly impermeable roots   Fine filters exclude sodium

  Control stomata & leaf orientation   Limits evaporation

  Anoxia   Prop Roots

  Pores within the bark

  Pneumatophores   “Snorkels”

  Large channels in plant   Transport oxygen quickly

  Nutrient Uptake   Sediments inside mangroves are anoxic

  Anaerobic bacteria   Produce sulphides, methane, phosphates

  “Mangrove Smell”

  Roots are able to absorb gases from atmosphere, rather than water

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Mangrove Communities   Root system creates habitat

  Underwater in sediments   Mud lobsters, shrimp

  Underwater on roots   Algae, barnacles, oysters

  Tidal Zone   Mangrove crabs

  Leaf waste feeds benthos

  On land   Coastal birds, fish

  Kangaroos!

Mangrove Food Web   Primary

Producers   Mangroves

  Consumers   Inverts   Fish   Birds

  Decomposers   Bacteria   Algae   Fungi

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Threatened Mangroves   “Mangroves more threatened than rainforests”

  200,000 km2 coastline   Found in 120 countries

  1-2% per year being removed   Urbanization   Aquaculture   Coastal Landfill

  Leads to –   Loss of Biodiversity   Coastal Erosion   Atmospheric CO2 sink lost   Economic value lost

  Fishing, tourism, etc.

Threatened Mangroves   Florida Keys

  Red, Black & White Mangroves

  23,500 acres removed (2001)   Dredging and filling in of coastline for waterfront

property

  Cropping to allow better views of water

  Problem?   Hurricane protection!

  State Regulations   $10K fine for removing mangroves

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Mangroves as a threat!   Invasive species!

  Seed pods good at long distance dispersal

  Ideal for instant growth

  Established on all Hawaiian Islands

  Red & Oriental Mangrove

  No natural predators to slow growth

  Replaced native marshlands

  Decline in native birds

  Increase in predators - mongoose

  Mangrove removal projects

Other Photosynthetic Habitats   Sea Grass Beds

  Not seaweeds

  Flowering plants

  Often grow in “meadows”

  Eelgrass

  Sand and mud bottom

  Anchor into sediments

  Form habitats

  Shelter & feeding grounds

  Fish, turtles, dugongs

  Molluscs, worms, nematodes

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Eelgrass   12 species

  Zostera

  Sandy substrates

  Particularly estuaries

  Stabilize sediments

  Traps flow

  Increases habitat for infaunal animals

  Used to be used for food

Conclusions

  Primary Producing Habitats   Coastal zones

  Kelp Forests   Features, threats

  Mangroves   Features, threats

  Food webs complex interaction – benthic, pelagic and terrestrial all together